The figures compiled by Ipsos Mori from the National Readership Survey show that in 1968, two-thirds of households were in the manual or lower-paid social grade bracket known as C2DEs. But by 2015, the proportion of C2DEs had shrunk to 45.8%.

Social grading divides up households based on the job of the highest income earner.

The grades range from A, people in upper managerial and professional roles, to E, which includes state pensioners, casual workers and the unemployed receiving state benefits.

Individual grades are usually grouped into brackets that combine several tiers, with ABC1s roughly described to be middle class, while C2DEs are broadly working class.

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Most of the change since 1968 has taken place in the middle brackets. Skilled manual workers (C2s) used to be the grade encompassing the highest proportion of UK households.

In the early 1990s, this group was overtaken by junior managers and professionals (C1s). C2s have since also fallen behind intermediate roles (the Bs).

Class, of course, is a pretty intangible concept and a person’s occupation will not cover all the intricate social constructions associated with it. Moreover, other measurements exist. The government, for example, uses a much more detailed breakdown called the National Statistics-Socio-Economic Classification.

Nevertheless, social grades do remain an incredibly strong predictor of a person’s lifestyle. The higher a person’s social grade the more likely they are to earn more and spend more. This makes the grades a useful tool for marketers who want to pitch a product to a certain demographic.

Another one of these areas is political analysis. For example, the largest electoral bloc in Britain are C1s. The Conservatives beat Labour among this grouping by some 15 points in both 2010 and 2015, suggesting that any future Labour success would probably need to close this particular gap.

Neil Farrer, the head of media measurement for Ipsos Connect, said: “These long term trends collected through high quality research provide a real insight into how the make-up of the country has developed over the past fifty years. Since we started collecting social grade, manufacturing in Great Britain has decreased significantly whilst there has been real growth in service related jobs ultimately leading to a burgeoning middle class. ”